On This Day in History

How it is calculated

The tool looks up a stored list of historical events for a calendar date. You give a month number (1 to 12) and a day number (1 to 31), and it builds the key month-day, for example 07-20. It then lists every event saved for that date as year followed by a short description, and shows how many there were. The lists are stored per language; if the chosen language has no entry for the date, the English list is used instead. If no event exists for the date, for example 31 April, no result appears. The number of events is not the same for each date or each language, and the entries come from a fixed dataset that is not updated live.

Common mistakes

• Typing the day first (20 then 7), as many countries write dates; the first box is the month, and a month of 20 returns nothing.
• Entering a month name or the year; only the month and day numbers are used.
• Trying a date that does not exist, such as 31 in a 30-day month.
• Treating the list as complete for a date; it is a selection of events, not every event that happened.
• Quoting dates in an essay without checking them in another source, as old dates are sometimes given differently across calendars.